Methods for interpreting data from x-ray crystallography to yield information about the structure of biological molecules including proteins and viruses will be further developed. These methods involve the use of a priori knowledge of substructures present in the molecules, and employ high-speed computer-implemented Patterson search. Compounds to be studied are organic molecules or macromolecules of biological interest. These include cholesterol monohydrate, Alstonia alkaloids, a flavoprotein, and Satellite Tobacco Necrosis Virus.